3.
ABSTRACT
According to a survey conducted by a mobile advertising researcher, AdMob, smartphone users
are driving up the use of Wi‐Fi hotspots. The result of the survey indicates that there were 550
million smartphone Wi‐Fi requests in Western Europe alone in 2008, a 132% increase for the
year. AdMob said that 42% of the requests from iPhones originated from Wi‐Fi hotspots [1]. In
the United States, AT&T reported a 41% increase for the year in iPhone connections, alone, at
wireless hotspots [2]. In a new report, the market research firm Yankee group [3] has forecast
that the number of smartphone users will quadruple to 160 million by the year 2013. In another
report released by ABI Research, Wi‐Fi smartphone sales will double by 2011 [4]. ABI Research
also found that 74% of people who have Wi‐Fi enabled smartphone’s use the technology and
77% say they want a Wi‐Fi enabled handset when they make their next purchase [5].
To summarize, we can foresee a huge growth in Wi‐Fi enabled smartphone’s in the future. The
important question to ask is whether the general public understands the security risks
associated with using a smartphone device in an unencrypted wireless hotspot. As an end user,
can they be certain that there is no security threat to their privacy and data when conducting
personal or corporate business from their smartphone, over a wireless network? In a published
article, Dan Hoffman describes how a computer can passively listen on a wireless network and
use the information to perform a man‐in‐the‐middle (MITM) attack to gain access to personal or
financial information. [6]. It is widely known that MITM attacks are a viable attack vector when
considering necessary precautions related to operating PC's in a wireless network environment.
The remaining question is whether the same types of precautions can be considered when
utilizing smartphone devices to perform similar tasks from the palm of your hand.
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INTRODUCTION
Let us consider a scenario, where a smartphone user connects to the Internet to determine if the
bank transaction is successful or not. The user is having a cup of coffee in a cafe, which happens
to provide a free Wi‐Fi hotspot. The user decides to use the free Wi‐Fi hotspot to connect to
online bank website and enters account credentials to log in to the site, directly from the
browser on his smartphone handset. The user successfully enters the online bank account and
verifies the transaction history. After finishing the work, the user log out and closes the web page
as requested by the online bank website. At this point, the user has no reason to suspect that
anything malicious occurred. The user finishes the coffee and returns to the office.
As is the current state of the technology surrounding smartphone devices, there are very limited
amounts of reputable applications that even address traditional information security concerns.
The reasons why the technology is lacking are wide ranging, but lead to one simple
conclusion...basic information security malware and anomaly detection capabilities are limited
to signature based malware detection.
Let us reconsider the same scenario from an attacker’s perspective. The attacker visits the same
cafe that offers a free Wi‐Fi hotspot and decides to employ basic host, network identification and
enumeration tools from the laptop to enumerate all the active devices connected to the Wi‐Fi
hotspot. From the results, the attacker notices a MAC address referring to a Nokia smartphone.
The attacker know that there is little to no detection capabilities present on an overwhelming
majority of smartphone’s in use today, so the owner would likely never find out about a
successful man­in­the­middle attack (MITM). The well‐informed attacker creates a successful
MITM attack. In the meantime, the smartphone owner accesses the online bank website and
enters the login credentials required to gain access to the banking information. In this scenario,
all of the communication between the smartphone and the online bank site is routed through the
attacker’s machine and the attacker can see the login details in plain text, as well as can capture
all the sites accessed by the victim.
Man in the Middle Attack (MITM)
A man‐in‐the‐middle attack intercepts communication between two systems by relaying
messages between them. In this attack, the attacker makes an independent connection with both
of the victim’s machines. The attacker machine forces the traffic between the victim’s machines
to route through it by sending a false ARP reply to both machines. The attacker can than create
new connections and kill existing connections, as well as view and replay anything that is private
between the targets machines.
In the following section we will discuss the tools used in implementing a MITM based SSL bypass
attack.
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TOOLS
The tools mentioned below are just a few of the possible tools that an attacker could use to
perform a successful MITM attack and break the security provided by SSL.
1) Arpspoof
It redirects packets from a target host on the LAN to the intended host on the same LAN.
It does so by forging the ARP replies to target host.
2) SSLStrip
Allows for the transparent hijacking of HTTP traffic on a network, watches for HTTPS
links and redirects, and then maps those links into either look‐alike HTTP links or
homograph‐similar HTTPS links. It also supports modes for supplying a favicon that
looks like a lock icon, selective logging, and session denial [7].
3) Ettercap or Wireshark
A multipurpose sniffer/interceptor/logging utility for switched LAN's. It is also used to
implement MITM attacks in the networked environment [8]. Whereas, Wireshark is a
network protocol analyzer and is often used as packet sniffer [9].
MITM ATTACK IMPLEMENTATION
The graphic displayed in Fig. 1 shows the network connection between an end user and the
router providing the connection to Internet before a successful MITM attack has been
implemented. Modern day web browsers regularly rely upon SSL certificates to ensure the
security of the data included in the encrypted communication between the browser and a secure
website.
As was proven in this year's BlackHat conference presentation “More tricks for defeating SSL” by
Moxie Marlinspike who authored the SSLStrip tool [10], it is entirely possible to defeat these
protections. The question remains whether this same vulnerability exists in the smartphone,
mobile computing world.
Figure 1: A schematic of wireless connectivity between handset and router.
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Utilizing the tools that were previously mentioned in this study, let us discuss how an attacker
performs a MITM based SSL bypass attack. Below, you will find the steps performed by an
attacker on the machine to perform a MITM attack designed to bypass SSL security. It is worth
mentioning that these particular tests were performed from Backtrack 4, pre‐release, but should
be the same when running under Ubuntu or other Linux distribution.
echo 1 > /proc/sys/net/ipv4/ip_forward
In this step, the attacker enables IP forwarding on his machine. By default, the value stored in
“ip_forward” is 0, which implies that IP forwarding is disabled. Changing this default setting to 1
enables IP forwarding
arpspoof ­i wlan0 ­t #victims ip address #router ip address
ArpSpoof forges ARP replies to the victim's machine. This step assumes that the attacker has
already determined the victim's IP address, utilizing some sort of network/port scanning tool
iptables ­t nat ­A PREROUTING ­p tcp ­­dport 80 ­j REDIRECT ­­to­ports 10000
The above command selects the Network Address Translation (NAT) table and appends the rule
to the PREROUTING chain. The rule is set for protocol "tcp" with destination port of 80 and it
sets the firewall to redirect all of the traffic coming in on port 80 to port 10000.
sslstrip ­a ­k ­f
The above command executes the SSLStrip tool and tells it to log all SSL and HTTP traffic to and
from the attacker machine.
ettercap ­T ­q ­i wlan0 or Wireshark
Finally, the attacker starts a sniffer to view the traffic going through his machine. The attacker
can use ettercap in text mode (‐T) to sniff only user name & passwords using (‐q) flag or can use
a tool such as Wireshark.
At this point, the attacker has successfully setup the machine to act as a man‐in‐the‐middle
between the unsuspecting smartphone and the Wi‐Fi hotspot. Utilizing this method, the attacker
has effectively told the victim device to route all traffic through the attacker's machine, and the
attacker machine then forwards the requests on to the Wi‐Fi hotspot. Since the attacker machine
now captures all the traffic from the victim smartphone, the attacker can kill or modify the active
connections. The attacker has already run the ssl bypass tool on the machine, thus as soon as the
victim accesses any email or online bank website, the login credentials will appear in plain text
on the attacker machine.
The fig.2 shows successful implementation of MITM attack.
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Figure 2: A schematic of successful MITM attack.
RESULTS
The following section discusses the results obtained on the test devices mentioned in Table 1. In
all of the test cases, the testing team set out to gain access to email credentials (user name and
password) as a means to prove a successful MITM attack against a smartphone device and web
server offering SSL security. For each platform, we tested these MITM attacks against different
email clients.
Name OS
Nokia N 95 S60 3 edition
Windows HTC tilt Windows Mobile 6.1 Professional
CE OS 5.2.19212
T­Mobile G1 Android
Apple iPhone 3G S iPhone OS 3.1
Table 1: List of test devices used in this study.
Nokia N95
For the N95 we test MITM based SSL bypass attack against three different email clients.
Web Browser:
We began by using the Nokia N95 web browser to access email. Fig. 3 consists of a screen shot of
the end user device and a screen shot from the attacker's machine. We can see from the screen
shot of the attacker's machine that the end user's login credentials are visible. The end user
continues to access the Internet unaware of the loss of privacy. The attacker can also use a tool
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such as “webspy” that will open all of the visited websites by the victim on to the attacker’s
machine.
Figure 3: The result from accessing email through browser.
Mailbox:
The second option to access email is by configuring the mailbox service found within the
messages folder on the device.
As in Fig. 3, Fig. 4 consists of screen shots from both the N95 and the attacker's machine. The
end user's email credentials are visible on the attacker's machine while the end user is setting up
an email account for the first time. The user's login information becomes available on the
attacker's machine whenever the user refreshes the mailbox.
Figure 4: The result from accessing email through mailbox
Xpress Mail:
The final application that is tested on the Nokia N95 is the Xpress Mail application. This
application encrypts the data between the device and the server in a manner that does not rely
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on SSL encryption between the client and the server. In this scenario, sniffing or SSL bypass
methods do not compromise the encryption provided by Xpress Mail.
Fig. 5 shows the screen shots from both the N95 and the attacker's machine. The screen shot
from the N95 shows the account setup step, whereas the screen shot from the attacker's
machine shows the sniffed packet that consists of encrypted login credentials.
Figure 5: The result from accessing email through Xpress Mail
Windows HTC tilt
For the Tilt, we tested MITM based SSL bypass attacks against three different email clients
Web browser: Internet Explorer
With the Tilt device, we initially accessed email through the web browser. Fig. 6 consists of
screen shots from the Tilt device and the attacker's machine. The screen shot from the attacker's
machine shows the sniffed user name and password from the Tilt device. As expected, the end
user is unaware of the fact that the login credentials are intercepted by the attacker's machine.
The attacker can also run “webspy” tool to sniff and open all the web pages accessed by Tilt user.
Figure 6: The result from accessing email through IE browser.
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Setup Email option in Messaging:
Tilt provides a native option for accessing email on the device. It is similar to mailbox option on
Nokia N95. Fig.7 shows the results and consists of screen shots from both the Tilt and the
attacker's machine. The attacker is using Wireshark to sniff packets and we can see that the user
name and password is visible in the captured packet. The Wireshark captures the same
information each time the end user refreshes the email client for getting new emails.
Figure 7: The result from accessing email through Tilt email client.
Xpress Mail:
The third option that we test for accessing email is the Xpress Mail client. The Xpress Mail
application provides end‐to‐end encryption between the device and the server. Fig. 8 consists of
the screen shot from the device and the attacker's machine. As expected, the user name and
password are encrypted. However, it cannot prevent interception of end user private
information for other websites, i.e. an online banking website from MITM attack.
Figure 8: The result from accessing email through Xpress Mail.
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Android G1
At the time of testing, the Xpress Mail client is not available for Android. Thus, we conducted our
MITM attack tests on two possible options.
Web browser: Default Android web browser
Fig. 9 shows the results obtained by implementing the MITM based SSL bypass attack on an
Android device. The result consists of screen shots from both the Android device and the
attacker's machine. We can see that the attacker was successful in sniffing the user credentials
and the end user remains oblivious of this sniffing attack on an Android smartphone.
Figure 9: The result from accessing email through Web Browser.
Figure 10: The result from accessing email through Android email client.
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Email Application:
The Android smartphone provides an email client similar to Windows Tilt and Nokia N 95 email
clients. The fig. 10 above shows email setup screen along with the sniffed credentials at the
attacker's machine. The attacker is able to sniff the login credentials, whenever the user
refreshes the email client application to update email messages on the smartphone.
Apple iPhone 3G S
The iPhone does not support Xpress Mail client at the time of testing. Therefore, we tested only
two ways of accessing email on the iPhone.
Web browser: Safari
The result in Fig. 11 shows the successful SSL bypass attack on the iPhone using the Safari web
browser to access email.
Figure 11: The result from accessing email through Safari Web browser.
Figure 12: The result from accessing email through iPhone email client.
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Email Application:
The native email client is the second option that we tested on the iPhone. It is similar to the
email client on the Tilt (Windows) or G1 (Android). Fig. 12 shows the results of the test, we can
see that the username and password is visible on the attacker's machine.
CONCLUSION
MITM attacks are considered to be a legitimate threat to confidential or private data in the PC
side of information security. The testing team has adequately shown that with a mobile laptop in
a Wi‐Fi network, it is possible to intercept communications between the smartphone and the Wi‐
Fi hotspot. The testing team was able to perform successful MITM attacks against four different
smartphone devices, illustrating that protections provided by SSL can be bypassed and login
credentials can be intercepted.
This study underscores the fact that the use of publicly available Wi‐Fi hotspots should be
approached with caution and care should be taken to ensure that confidential or private data is
adequately encrypted, when it becomes necessary to access such data. Where possible,
smartphone users should seek out and identify applications that provide adequate encryption
technologies to protect confidential or private information. At this point, such applications do
exist, but are scarce. When selecting applications to handle sensitive communications, users
should search for applications that provide end‐to‐end encryption between the client application
and the end server. Additionally, when dealing with applications that provide access to financial
institutions or other sensitive information, the same precautions should be taken to ensure those
communications are encrypted end‐to‐end. When such applications are not readily available,
users must ensure they take necessary precautions to ensure they are only accessing sensitive
information over, either, the service provider's internet connection provided from their data
plan or from a trusted, secure Wi‐Fi network, where available.
Additionally, personal smartphone users and enterprises providing (or allowing) smartphone
access into their environments for productivity, should ensure that security software is installed
that provides firewall and anti‐virus capabilities, at the least. Users and enterprises must begin
to treat their smartphone devices with the same care that they do when using their PC's or
laptops. The threats, while not as extensive at this point, are quite similar and costly when
successful attacks occur. Moreover, as always, as vulnerability/exploit research continues to
occur against smartphone devices, so to will the number of exploits that translate into successful
attacks against smartphone users.
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